Durban Retinal AssociatesDurban Retinal Associates

Many patients will be aware of small “black spots” in the field of vision in one or both eyes.  The following article explains the causes of this phenomenon and when to seek medical advice for this common symptom:


Most people at some time will be aware of small black shadows in the vision of one or both eyes, especially when looking at a pale surface like a white page, a bright sky or perhaps when walking on the beach.  These are called floaters.  These black spots are impurities in the fluid that fills the back cavity of the eye.  This jelly fluid is called the “vitreous” and is a thick fluid which has a consistency similar to “egg white”.  This vitreous fluid is present in the eye from birth, and is not replaced or exchanged during life.  It is initially attached to the surface of the retina, which is the light sensitive nerve tissue layer that lines the back surface of the wall of the eye.

It is important to note that it is not necessarily abnormal to see black spots in the vision.  The size and number of floaters seen is variable; some patients (especially short sighted people) will be aware of numerous floaters, whilst others may never be aware of the symptom at all.

Some floaters can interfere severely with vision, while others are barely noticeable.  Although annoying, floaters are usually harmless, and come and go over the years.


It is not uncommon for some patients to be aware of small “flashes” of light at times.  They may or may not be associated with the appearance of new floaters.  Flashes are usually caused by the vitreous body tugging on the retina.

This tugging occurs when the vitreous body shrinks as a normal part of the ageing process.  Flashes may last for a few seconds or several minutes, and can occur off and on for weeks or months.  They are usually seen at night or in poor lighting.

(Migraine headache can cause the perception of similar light flashes although often these flashes of light may have numerous colours.  The abnormal light flashes seen with migraines are usually very different, appearing as jagged lines blocking an area of vision or moving slowly across the field of vision in one or both eyes.  People who suffer from migraine headaches will often know the familiar pattern of these visual phenomena, often occurring just before the headaches begin.  These migraine flashes are unrelated to the vitreous body and its attachment to the retina).

Floaters and Flashes

In some cases, the sensation of seeing floaters and/or flashes may be an important warning sign.

The vitreous is composed of collagen, which is the chemical substance seen in other parts of the body(for example the skin).  Collagen undergoes structural changes with age, and will become more liquid like and watery in later life.  At some point, the chemical bonds that link the vitreous fluid to the surface of the retina will become weaker and the vitreous jelly will separate from the retina.  This process is called a POSTERIOR VITREOUS DETACHMENT or P.V.D and is a normal consequence of ageing.  Approximately half of all people will have a PVD in one or both eyes by the age of 60.

When this occurs, the patient will typically be aware of the sudden onset of new floaters, often associated with flashes of light.  This may vary from a few new black spots, to a fairly dramatic impression that one seems to be looking through a “lace curtain”.  A large floater, often oval or C-shaped is often seen.  Although initially quite dramatic, the symptoms will usually gradually fade over 3 to 6 months.

Unfortunately, the vitreous body is sometimes more firmly attached to the surface of the retina and may pull away a piece of the retina or tear the retina as it separates.  This can cause slight bleeding, triggering what people often describe as a “shower” of new floaters.

When these retinal tears happen, fluid can escape, pushing the retina off the inside of the eye.  This is known as retinal detachment, which is a serious threat to sight.  Surgery is needed to reattach the retina if a retinal detachment occurs.


See your ophthalmologist if new floaters appear, with or without sudden light flashes.  Any loss of peripheral (side) vision should be investigated without a delay.
Your ophthalmologist will give you a complete eye examination.  Drops are put on the eyes to enlarge the pupils.  An ophthalmoscope is used to examine the vitreous body, retina, blood vessels and other structures.  Your ophthalmologist will be able to diagnose whether posterior vitreous detachment, retinal tear, retinal detachment or bleeding is present.

People who have occasional floaters and flashes should have annual eye examinations.

Symptoms of a posterior vitreous detachment (PVD) most often occur in one eye at a time.  Even though your ophthalmologist will check both eyes at the first visit, it is important to realise that if similar symptoms are experienced in the other eye, you should see your ophthalmologist again with the onset of new flashes or floaters as you could be having a PVD in this eye.  As complications occur at the time of PVD, it is important to review with new symptoms as it is not possible to determine which patients will develop a retinal tear at the time of posterior vitreous separation.


Floaters and flashes are usually just annoying, not harmful.  However, they can be signs of serious problems (like a tear to the retina) and, for this reason, must not be ignored.

For most people, treatment is not necessary.  Floaters and flashes usually subside over time, causing no permanent deterioration to vision.  Wearing sunglasses when driving or reading may be helpful.

The sudden onset of many new floaters or flashes must be taken seriously.  You should seek immediate advice from your ophthalmologist.  It can be a warning of looming serious eye problems, including tears of the retina or a detached retina.

Treatment of Flashes:

Light flashes caused by posterior vitreous detachment do not need treatment if the retina is not torn.  If a retinal tear is present, however, early treatment to seal it can prevent retinal detachment.  A tear may be treated by either or both of the following:

  • Laser treatment (photocoagulation).  The laser beam is directed through the pupil and focused on the part of the retina that is torn.  As tiny burns made with the laser heal, the scar tissue seals the tear, similar to “spot welding”.
  • Cryotherapy (freezing treatment).  A small probe is applied to the outside of the eye. Extreme cold freezes through to the retinal tear.  This creates scar tissue that seals the hole.  Cryotherapy is usually only necessary if the tear is in a part of the eye that is not amenable to laser treatment or if blood in the vitreous prevents adequate view for laser.

Both treatments are usually performed using local anaesthesia and can cause slight discomfort.  There is a small risk of reduced vision and a possible need for further treatment, including retinal detachment surgery.  However, this risk is much lower than the risk of vision loss due to leaving the retinal tear untreated.

If you require surgery for a detached retina, your ophthalmologist will have more information about the benefits, risks and limitations of treatment.

Treatment of Floaters:

Large and persistent floaters that obstruct vision can be surgically removed during a procedure known as a vitrectomy.  Vitrectomy surgery has its own risks and considerations and is not recommended unless the floaters are causing severe symptoms that interfere with normal function. Vitrectomy surgery is performed in the operating theatre under general or local anaesthetic.  Special instruments are used to remove the floaters, along with some or all of the vitreous fluid.  The vitreous is usually replaced with a clear salt solution; rarely, a synthetic gas or silicon oil may be used.  Vitrectomy surgery is usually performed under local anaesthesia or, occasionally general anaesthesia.

As possible complications can be serious and may not be worth the risk, vitrectomy surgery is recommended only in unusual cases.  Complications can include retinal detachment, cataract formation, glaucoma and ultimate loss of vision in the operated eye, among other possible side effects.  However, vitrectomy surgery may be an acceptable option if floaters drastically affect driving, reading or the ability to work.